for the remaining holes or groups of holes, or flow circuits. The process is repeated with various holes or passages blocked until all desired measurements have been made. Comparisons to either gauge measurements on reliable parts or to analytical models of flow circuits determines the acceptability of the parts. However, the technique is known to be time consuming resulting in a check of only selective film holes, groups of holes, or flow circuits. Additionally, the technique has the propensity to overlook local or individual features or holes that are out of specification.
Other techniques include dimensional gauges, for example pin checks, and other visual methods, for example water flow. Industry typically relies on these methods to determine the quality of each part as compared to a nominal standard part or a specification. Certain types of interior wall flow holes or orifices can be inspected by means of boroscopes, but only when the dimensions of the access regions within the parts are large enough. Non-destructive inspection methods, such as ultrasound and x-ray, are used to detect material flaws and dimensions, but are limited to the immediate surface and wall under the inspection device. Accordingly, ultrasound and x-ray inspection techniques cannot detect across a void to an interior wall, and, as such, are not applicable for inspecting blind flow holes in integrally cast components.
Thermal transient methods are used to detect material flaws, voids, thicknesses, and external surface hole depths, but again operate only on the immediate wall beneath the detection device. Commonly assigned U.S. Pat. No. 6,804,622, Bunker et al., entitled “Method and apparatus for non-destructive thermal inspection,” discloses the use of transient infrared thermal imaging to measure the heat transfer coefficients on the interior surface of an exterior wall. However, the heat transfer coefficients do not, by themselves, provide a quantitative measurement of the fluid flow through blind holes, nor do they provide a quantitative measurement of the cross-sectional area of the blind holes.
It would therefore be desirable to provide a non-destructive inspection method and system for quantitatively measuring the flow rate and cross-sectional area of interior blind flow holes.